The root-knot nematode Meloidogyne hapla is a major pest in organic farming causing severe damage especially on vegetables. Common practices such as high cropping frequencies of legumes and low frequencies of cereals in association with unsatisfactory weed control are assumed to be major factors for nematode build-up. Due to the broad host spectrum of M. hapla strategies solely based on crop rotation are often not sufficient in controlling the nematode. A series of field experiments was conducted to develop more efficient control strategies. Based on the results a recommendation for reducing high nematode densities was developed which is build on black fallow throughout the main vegetation period buffered by additional measures such as previously growth of a overwintering legume and its incorporation early in spring before the nematode has multiplied and followed by a overwintering cereal to conserve soil nutrients and avoid erosion. In the long-term any build-up of damaging levels of M. hapla need to be avoided by a higher cropping frequency of non host crops (e. g. cereals, Tagetes), growth of catch crops (e. g. fodder radish), satisfactory weed control, short periods of black fallow to allow the soil to rest and avoidance of clover immediately before growing susceptible vegetables
